Tanning material.



UNITED STATES RHINE, GERMANY, A CORPORATION.

PATENT OFFICE.

OTTO SCHMIDT AND JULIUS MULLER, OF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, I

ASSIGl-NORS T0 BADISGHE ANILIN & SODA FABRIK,

OF LUDWIGSHAFEN-ON-THE- TANNING MATERIAL.

To all whom it may concern Be it known that we, O'rro SCHMIDT and JULIUs M'tiLLER, subjects, respectively, of the King of Prussia and theKing of Bavaria, residing at Ludwigshafen on the Rhine, Germany, haveinvented new and useful Improvements in Tanning Materials, of which thefollowing is a specification.

. In the Annalen dew Ohemie (vol. 178, 1875, pp. 171 et seq.) Schifi'has described the production of condensation products from'phenol-sulfonic acid by heating it either with a large excess ofphosphorus oxychlorid at from 50 to 60 0., or by itself at about 200, C.at ordinary pressure, and states that theproducts are solid, andinsoluble in dilute acids, and that," when used as tanning agents, theyconvert skins into a brittle leather. The leather obtained ispractically Worthless and consequently the compounds described by Schiflhave not been used commercially for tannin".

We have now found that by heating a phenol-sulfonic acid under mildconditions we can obtain products which, in contradistinction to thosedescribed by Schifi', are eminently adapted for use as tanning agentsespecially in the manufacture of leather. Under "the term aphenol-sulfonic acid we include the sulfonic acids of phenol and ofhomologues thereof, particularly the cresols. During the production ofthe new compounds, water is split 0H and condensation takes place, andWe prefer, especially in the case of using phenol-sulfonic acid, tocarry out the condensation under diminished pressure. If desired, acondensation agent '(such for instance as phosphorus trichlorid,phosphorus oxychlorid, or thionyl chlorid) can be added, during thereaction, or, if desired, the products obtained by condensation withoutt e addition of such an agent can be subsequently treated therewith.When employing phenol-sulfonic acids, no excess of the condensationagent should be employed, since otherwise products may be ob tainedwhich, like Schiifs aforesaid prod- Specification of Letters Patent.Application :flled January 21, 19-13.

Patented MarnlO, 191st. Serial No. 743,297.

nets, are not suitable for tannin" purposes. When working withphenol-sulfonic acids at ordinary pressure, the temperatureshould notexceed about 150 C. for any length of time. When producing tanningagents from cresol sulfonic acids, the conditions obtain ing need notalways be so mild as is desirable in the case of phenol sulfonic acids.

The products obtained according to this invention are probably bodieswhich are less' highly molecular than those obtainable according to themethod described by Schitf, and, when employed for tanning skins orhides, full white leather of great softness and pliability can beobtained. As a general rule, the products of this invention are thicknon-crystallizable syrups, but some approach a solid state on beingcooled and a few of those obtained from cresol sulfonic acids can beobtained in the solid state. Their alkali salts are colorless, amorphousand readily solublein water, yielding intense colorations with ferricchlorid and iron alum and, after the addition of acid, coagulate gumsolution. The free acids are also generally soluble in dilute acids.Either the free acid or the alkali salt, in the presence of acid, issuitablefor tanning skins or hides, and they can be used, if desired, inadmixture or conjunction with other tanning agents. Our new tanningagents contain sulfur and are also practically free from diphenylmethanecompounds; consequently, on treatment in cold aqueous and slightlyalkaline solution with a small quantity of alcoholic tetrachlorquinoue,no coloring matter is formed.

The following examples will serve to illustrate further the nature ofthis invention, which, however, is not confined to these examples. Theparts are by weight.

Example 1: Heat phenol para sulfonic acid at a pressure of 20 mm. and ata temperature of 130 0., for about 24 hours, or take test portions fromtime to time, dissolve them in water and add gum solution. When theprecipitation which then occurs no ample.

' in the cold, see

longer increases in quantity, the reaction is finished. The reactionproduct can be directly employed for tanning, or it can be purified bydissolving it in water, neutralizing with caustic soda solution,filtering and evaporating the filtrate to dryness, whereupon a whitepowder is obtained which rapidly dissolves and gives a clear solution inwater. By ferric chlorid, the aqueous solution is colored red-violet.After acidification, it gives a considerable precipitate with gumsolution. Skins or hides which have been tanned with a solution of theacid, or the acidified salt, are colored orange by iron alum.

Example 2: Heat, for 7 2 hours, at a pressure of 20 mm. and at atemperature of 140 (3., the product obtained by heating phenol gentlywith concentrated sulfuric acid, which consists principally ofphenol-parasulfonic acid together with some phenolortho-sulfonic acid.Work up the reaction product as described in the foregoing ex Example 3:Heat ortho-cresol-sulfonic acid (obtainable by sulfonating orthocresolBerichte 20, 3210) at a pressure of 20 mm. and a temperature of 130 C.,for about 24 hours, or until a test portion, on being dissolved in waterand on the addition of gum solution, shows that no further increase inthe precipitation takes place. Then take up the product with water,filter,- neutralize the filtrate with caustic soda and evaporate todryness. The product is readily soluble in water and the solution iscolored' red-violet by ferric chlorid. After acidification, it yields aconsiderable precipi- -tation with gum solution. By heating the productwith dilute sulfuric acid, cresol is split off.

Example 4: Heat 1,000 parts of crude cresol-sulfonic acid at a pressureof about 20 mm. and at a temperature of 130 0., for about 24 hours,until a test portion shows that the reaction is complete. Then cool toabout 80 C., add 186 parts of phosphorus trichlorid and stir for 1 hourat this temperature and at ordinary pressure. Then take up the productwith ice and water, allow it to stand for some time and work up asdescribed in the foregoing Example 3.

' The product is similar to that obtained according to the said Example3.

Example 5: Heat together 3 parts of crude cresol-sulfonic acid and 1part of paraphenol-sulfonic acid for 48 hours in cacao, at a temperatureof 133 C. When the mixture is cold, dissolve it in 18 parts of Water,allow the solution to stand for some hours, filter it and then nearlyneutralize the filtrate, so that about 5%of acid remains unneutralized.Cool in ice for 2 hours, filter weave? and evaporate to dryness. Theproduct thus obtained is a light brown mass which rapidly dissolves inwater and gives a copious precipitation with gum solution.

Example 6: Heat 225 parts of the sulfonation product of crude "cresolwith 262.5 parts of phosphorus oxychlorid for 4 hours at 60 G. Thendistil off the excess of phosphorus oxychlorid, and wash the productwith hydrochloric acid.

Example 7 Dissolve,1n water, the product obtained according to .theforegoing Example 3 and, if necessary, acidify it slightly, but not tosuch an extent that the skins or hides swell too much. The solutionshould have a density of about 0.6 B. Then hang the well-limed and batedskins or hides in the solution andgradually increase the quantity oftanning material and acid until, at

the end of 10 days, the solution has a density of about 5 B. The processof tanning requires about 14- days. The leather is then neutralized andtreated with fat and dried, which 'may be done in the usual manner. Theleather is of excellent quality and does not become brittle on drying.

Either but one tanning bath can be employed or a series of two, three,or more such baths of difierent strengths can be employed, so that theskins or hides are subjected to the successive action of strongertanning solutions.

Instead of employing the hanging process, the skins or hides can betanned in other manner, for example according to'the paddling process,or in a drum, and in these cases the tanning liquid is preferablyemployed, from the start, in a more concentrated form, for instance from2 to 4 B., and is subsequently also gradually strengthened. In this waycomplete tanning can be efiected in from 6 to 8 hours, according to thematerial being tanned. In a simllar manner, the tanning materialsobtained according to others of the foregoing examples can be used fortanning.

Now what we claim is 1 1. As new articles of manufacture condensationproducts obtainable from a phenol-sulfonic acid, which new compoundscontain sulfur, are practically free from diphenylmethane compounds, andin the form.

ferric chlorid and, after the ad- 1 sulfuric acid splits ofi' cresol,and in the set our hands in the presence of two subform of its alkalisalts is practically colorscribing witnesses.

less, amorphous and readily soluble in Water OTTO SCHMIDT yieldingsolutions which give intense c0lorations with ferric chlorid and afterthe addi- JULIUS E tion of acid coagulate gum solution, and Witnesses:

which tan hides giving a useful leather. JOSEPH HEIFFER,

In testimony whereof We have hereunto J. ALEC. LLOYD.

